Fix kwargs syntax for Python 2.x
Fix kwargs syntax for Python 2.x

cupy/cupy,ronekko/chainer,hvy/chainer,okuta/chainer,chainer/chainer,wkentaro/chainer,keisuke-umezawa/chainer,ktnyt/chainer,hvy/chainer,ktnyt/chainer,cupy/cupy,hvy/chainer,hvy/chainer,jnishi/chainer,jnishi/chainer,niboshi/chainer,chainer/chainer,niboshi/chainer,ktnyt/chainer,pfnet/chainer,okuta/chainer,chainer/chainer,keisuke-umezawa/chainer,cupy/cupy,cupy/cupy,aonotas/chainer,niboshi/chainer,niboshi/chainer,jnishi/chainer,anaruse/chainer,ktnyt/chainer,jnishi/chainer,tkerola/chainer,keisuke-umezawa/chainer,kiyukuta/chainer,delta2323/chainer,wkentaro/chainer,wkentaro/chainer,rezoo/chainer,kashif/chainer,ysekky/chainer,wkentaro/chainer,chainer/chainer,okuta/chainer,okuta/chainer,keisuke-umezawa/chainer